Later in the day Kurt Blandin stalked into the News office and went directly to Tim’s desk.

“Too bad about Dugan,” he said, but there was no pity in his words. “I didn’t see him until we struck. I’d thought of bringing the air circus back here, but I’m not so sure about it now. The accident will give us kind of a black eye.”

“You don’t seem to be very sorry about what happened to Dugan,” snapped Tim, his eyes steely and his lips drawn in hard lines. “And Blandin, I don’t think we want you around here. There are a lot of things you are going to have to explain. I’ve got a few suspicions about you that aren’t very pleasant—Sky Hawk!”

The last words fairly ripped between Tim’s lips. Tensed, the flying reporter watched their effect on Blandin. The head of the Ace air circus swayed like a slender reed in the wind, but there was no change in the mask-like expression of his face. Perhaps his eyes shifted slightly, but that was all. He laughed, a cold, nerve-chilling laugh that shocked Tim’s finer sensibilities.

“You’re crazy, Murphy,” replied Blandin and before Tim could reply, turned and hurried from the room.

For half an hour Tim remained at his desk, mulling over the events of the last months. Only a few hours before he had been so near the solution—so near to learning the identity of the Sky Hawk. If Dugan could only talk, but Dugan’s lips were stilled forever.

The daredevil’s words about the German ace came back to him and he went into the library in the News building and sat down before a large file. Slowly he thumbed through the orderly stack of pictures with their descriptive stories attached. Back through the years he went as he rejected first one picture and then another.

Suddenly he stopped. The picture in his hand was familiar. A face was smiling up at him from the glossy print, a German fatigue cap was set at a jaunty angle, there was a slight scar over one eye—it was familiar and yet unfamiliar. It looked like Kurt Blandin, yet it was unlike Kurt Blandin. It might have been Kurt ten years before.

Hastily Tim read the short paragraph of descriptive matter attached. The picture in his hand was that of Max Reuter, one of the greatest of German aces, who had been brought down behind the Allied lines just before the close of the war. Shell-shocked, Reuter had been held in a prison camp until the close of the war and then released.

The clipping told little more of importance, but to Tim it had provided a world of information. The whole puzzle fitted together. Dugan’s story, even without him, was complete, and he hurried from the library and started toward the municipal airport.

Tim had a premonition of danger and when he reached the field was not surprised to see Hunter run toward him the minute he came through the gate.

“Tim, Tim,” cried the field manager. “The Sky Hawk has struck! He’s wrecked our eastbound express plane and looted its cargo!”

“Where?” asked Tim with a numbness of heart that seemed to weigh him down.

“East of Montour. The report just came in. It couldn’t have happened more than an hour ago. Ralph’s over on the line now warming up your ship. Will you help us out?”

Tim nodded, hastened into the office for a suit of coveralls and in five minutes was speeding west. Less than an hour later they were scudding to a landing on a field where the remains of the eastbound express were only a blackened heap.

It was a simple story. The country was sparsely settled. A forced landing by the plane, a pounce by the waiting Sky Hawk, a dead pilot, a flaming plane with empty express compartments. The marks of the Sky Hawk’s plane were plainly visible in the snow, even his footprints could be discerned. But that was all There were no fingerprints, nothing more than the tracks in the snow. It looked like a hopeless quest when Ralph, poking around in the wreckage of the plane, picked up a bit of metal. It was a small piece of copper, corroded, strangely so.

Without explaining his action to Tim, he pocketed it and they prepared for the return flight to Atkinson.

“Find out anything?” demanded Hunter who was waiting for them when they landed.

“Not much,” said Ralph, “but I’m going to ride the westbound plane tomorrow morning. Maybe we’ll know more then.”

“What’s this theory about the Sky Hawk you’re working on?” asked Tim when they were alone.

“It’s hardly a theory,” admitted Ralph. “A hunch maybe, but not a theory. Look at this.”

He pulled the chunk of corroded copper from his pocket.

“It’s one of the cabin fittings,” said Tim recognizing the piece from the wrecked plane, “but what of it.”

“Nothing much,” replied Ralph, “except it holds the secret of the Sky Hawk’s power.”

“What! You’re crazy.”

“No, I’m not crazy. It’s as plain as day. You wait and see.”

“I’ll wait, all right,” agreed Tim. “Either you’re awful bright or I’m awfully dumb. But this is your show. You must have a good idea of how the Sky Hawk is bringing down these planes. Here’s luck.”

The next morning found them at the field, ready for the departure of the westbound express. Hunter, worried and anxious, was on hand. Every plane which the Sky Hawk destroyed meant a loss of $25,000 and he could see a year’s profits gone in a week unless someone solved the secret of the Sky Hawk’s power.

Tim was warming up the Good News but turned for a final word from Ralph.

“Fly high and keep well behind us,” instructed his chum. “If anything goes wrong with our ship, cut your motor, listen for the hum of another plane, but don’t try to follow it. Beat it for the ground and pull what’s left of us clear of the machine.”

“And don’t,” he added as an after thought, “dive through any queer looking clouds which may be near our plane if we’re struck down.”

With that Ralph hurried into the cockpit of the waiting express ship where he crowded in beside the pilot. In another minute both planes were winging their way into the west, the motors barking in the cold winter air.

The trip was uneventful and four hours later the planes roared down on the snow covered field at Lytton, the western terminal of the transcontinental’s southwestern division.

“Too clear. We need clouds to catch the Sky Hawk,” was the only explanation Ralph would make when Tim asked him about the trip.

The next day Ralph looked at the winter sky, studded with scurrying wind-swept clouds.

“We’ll go with the express,” he informed Hunter over the phone. “The Sky Hawk will strike today and we want to be on the job.”

Ralph lapsed into a grim silence as Tim and the pilot of the express ship prepared their planes for the takeoff on the eastbound trip. Within a few hours, perhaps minutes, the Sky Hawk would strike again. Just where and how he could only guess. He was pitting his nerve and brains against the craft of a master crook. The decision was in the balance.

Ralph conferred with Tim for a moment before he crowded into the cockpit of the express plane. Then the two ships whirled over the snow and into the air.

An hour, two hours elapsed and the planes were speeding over the desolate Rock river country.

Tim, above and behind the mail, suddenly saw the express plane wobble unsteadily and then drop away in a sickening dive. Remembering the instructions Ralph had given him, he cut the motor of his own craft, and glided noiselessly through the broken clouds. He thought he heard the faint hum of a motor—a higher pitched note than that of the express plane’s engine. It was gone in a second and he turned his attention to the express plane, fluttering helplessly toward the ground.

With motor on full, he crashed downward through the clouds in a screaming power dive. Every strut on the Good News shrilled its protest but he held the nose down. He must reach the ground with the express; must be able to help Ralph and the express pilot if they needed his assistance.

The express was limping toward a small clearing and Tim, now under it, leveled off and made a fast landing. A ground loop slowed his speed and he was running toward the express plane when it banged down into the snow, its landing gear crumpling as the pilot made clumsy attempt to land. The plane flipped over on its nose and a figure was thrown clear of the wreckage.

Tim reached the limp form on the snow. It was Ralph! But there was no time to ascertain how badly his chum was injured. There was a sizzling flash, a roar, and the motor of the express was enveloped in a mass of flame. Tim plunged on and under the overturned fuselage. There, still strapped in his seat, he found the unconscious pilot. With anxious hands he unfastened the safety belt and dragged the man away from the flaming craft.

When he returned to Ralph, he found his chum gasping for air but otherwise unhurt. Together they worked to bring the express pilot back to consciousness.

“What happened?” demanded Tim.

“The Sky Hawk almost got us,” said Ralph, his voice husky and unnatural. “Another ten seconds and our goose would have been cooked. Here, let’s get this chap in the Good News. We’ve got to get him to a doctor quick. I’ll tell you all about it on the way to Atkinson.”

When they were safely on their way to the home field, Ralph explained what had happened.

“He gassed us,” he said simply. “That’s the secret of his power to send planes and pilots to their destruction. He only strikes on cloudy days when he can hide in the clouds. Just before his intended victim comes along, he releases the gas in the clouds. The unsuspecting pilot runs right into the gas and puff! That’s all there is to it. Simple, isn’t it?”

Tim was speechless with the horror of the Sky Hawk’s method.

“Simple, yes,” he managed to say, “but terrible.”

“I’ll admit that,” grinned Ralph, and after tomorrow, if the weather’s cloudy, there won’t be any more Sky Hawk.

“What do you mean?”

“That we’ll get the Sky Hawk. Now that we know his methods, we have the upper hand. This terror of the skies is about at the end of his string.”

When they landed at Atkinson a doctor quickly brought the express flyer back to consciousness although he was rushed to a hospital for treatment to check the ravages of the gas which he had breathed. Ralph had been lucky and the slight whiff he had gotten had knocked him out only temporarily with no lasting danger.

They reported to Hunter, studied the weather forecasts for the next day, and completed their simple preparations for the capture of the Sky Hawk.

The morning edition of the News carried a carefully worded story how a special plane was to leave Atkinson that morning on a dash across the plains with a heavy shipment of specie needed by a bank at the western terminal of the division. The $1,000,000 plane, the paper called it.

When Tim and Ralph wheeled the Good News from the hangar that morning, a truck was coming through the main gate with uniformed policemen on the running boards. It was the work only of a minute to transfer the two dummy specie chests, heavy iron-bound boxes, from the truck to the cabin of the Good News. They were leaving nothing to chance for the Sky Hawk might have accomplices on the field.

After a word with Hunter, Tim gunned the motor of the Good News and they raced across the field and into the air in quest of the Sky Hawk. Both boys were concentrating on the task ahead.

When they neared the Rock River country Ralph nudged his companion.

“Better put on the gas masks,” he warned. “The clouds are heavy ahead of us; just the place for the Sky Hawk.”

They donned the gas protectors, ready for the Sky Hawk to strike. Ahead of them loomed a cloud, grayish-green in color.

Ralph signed for Tim to cut the motor. They soared silently. To their right and ahead of them they could hear the sound of another plane. Tim turned on his motor and ruddered hard to the right. All around them were the grayish-green clouds of gas. The Sky Hawk had laid a careful trap for the specie plane.

Suddenly they broke through the clouds. Just ahead of them a sleek, black monoplane was loafing in the sky. Its pilot, startled at the sudden appearance of the Good News, was caught unawares, and they were almost on him before he could rev up his motor.

As they roared down on the monoplane, they caught a glimpse of the pilot, his face covered with a hideous mask to protect him from the gas clouds which he had scattered through the sky.

It was the Sky Hawk, the terror of the airways!

With quickening pulse, Tim set himself to the task of riding the Sky Hawk to earth. He knew his plane was faster than that of the aerial bandit, but could he match his skill with the enemy and force him to earth?

There was a puff of smoke under the fuselage of the Sky Hawk’s plane and another of the gray-green clouds took form. But Tim and Ralph were protected from the gas and they drove through the cloud in a burst of speed.

The Sky Hawk looked around, plainly alarmed. He had evidently believed their, first appearance pure luck but their escape this time was no such thing and the sky bandit realized that he was cornered. He could fight or run and either way the odds were against him for the Good News was too speedy for his craft. The tables were turned on the Sky Hawk. For the first time he found the odds against him and he chose to run.

It was a game to Tim’s liking and he roared down on the tail of the black monoplane. Both Tim and Ralph were armed but they hesitated to use their guns except as a last resort.

On and on they roared, first zig-zagging to the right, then to the left, up, then down, always on the tail of the sky Hawk, driving him ever nearer the ground.

Desperate, the masked bandit in the black plane turned on them and bullet after bullet ripped through the air as he blazed away at Tim and Ralph with a sub-machine gun. It was dangerous work now, but Tim handled the Good News in masterful fashion relentlessly teasing the Sky Hawk into shooting at them when they had him at a disadvantage.

Finally the sky bandit threw away his gun, his ammunition exhausted. Tim saw the gesture and steeled himself for the end. Whatever its outcome it would come quickly.

The Sky Hawk threw his plane into a crazy, twisting climb that threatened to pull the motor out of the ship. Tim outguessed him and climbed two feet to the bandit’s one. Two, three, four, five thousand feet they clawed their way into the sky, the Sky Hawk trying frantically to escape his pursuers for in the grimfaced flying reporters he could read his finish unless escape came soon.

Ralph had put together the tangled webs which put them on the Sky Hawk’s trail. Now it was up to Tim to bring about the end of the career of the gangster of the airways.

“Hang on,” yelled Tim as he pushed the throttle to the end of its arc. The song of the motor deepened and the Good News quivered as it felt the full power of the 500 horse power engine.

The Good News dropped down on the Sky Hawk’s ship like an avenging eagle. It swooped low, ready for the kill.

Closer and closer came the motor-maddened planes, each pilot intent on the destruction of the other. Then, too late to escape, the Sky Hawk guessed Tim’s plan but before he could move or throw his plane into a spin, there was the crash of wood and the scream of wires.

Half of the upper wing of the monoplane crumpled as Tim raked his landing gear through it. The propeller shivered into a thousand pieces and the motor raced madly.

Tim and Ralph, peering from their plane, saw the black craft pause in mid-air for a moment. In that fleeting second they saw the Sky Hawk half rise in his cockpit and rip the gas mask from his face.

It was Kurt Blandin and in the anger-marked face Tim recognized the likeness to Max Reuter, the German ace. The mystery was solved, the puzzle fitted and Blandin punctuated its completion with a final show of bravado as he raised clenched fists toward them.

Then the black plane fell away in a tight spin. Blandin made no effort to escape and a thousand feet above the ground the wings collapsed and the Sky Hawk crashed to his death.

Tim swung the Good News in a great circle, then headed for Atkinson. The Sky Hawk was gone; the airways were clear once more.